1. Field of the Invention
The present invention relates to a portable radio apparatus such as a pager, a portable telephone, a personal handy phone system (PHS) and others, and more particularly to a portable radio apparatus having a display portion.
2. Description of the Related Art
Recently, spread of a portable radio apparatus is remarkable owing to the multimedia boom. There can be exemplified a pager, a portable telephone, a PHS and others as a portable radio apparatus. This type of portable radio apparatus is usually provided with a display portion for displaying a message to a carrier. As a method for displaying a message in a display portion, the following two schemes can be considered.
One is a method for continuously displaying messages in a display portion irrespective of attachment/detachment of a portable radio apparatus or enabled/disabled operation.
The other is a method for erasing a part or all of the displayed messages in a display portion when a predetermined time lapses after an operation switch of the portable radio apparatus is pushed by a carrier.
On the other hand, a technique relating to the display portion in an electronic wristwatch is disclosed in, for example, Japanese utility model laid-open publication No. Sho 59-037587 although it is different from the portable radio apparatus. In this electronic watch, a temperature detector makes judgment upon whether the watch itself is worn on a wrist of a user. If a result of judgment is "NO", control for erasing the displayed message in a display portion is carried out.
Of the above-mentioned two displaying methods in the related art portable radio apparatus, however, the standby time is longer than the operating time and the message is always displayed in the display portion in the former case. Therefore, the consumption current used for this displaying operation is increased, which results in an extremely-short duration of life of a battery.
In the latter portable radio apparatus, a part or all of the displayed message is eliminated irrespective of use/non-use of the apparatus when a predetermined time lapses after the operation switch is pushed. A standard of judgment upon whether the carrier is really using the apparatus is therefore vague. For example, it is assumed that the portable radio apparatus displays a current time in the standby mode. In order that the carrier confirms the time, it is enough for him/her to just take a look at the display without need to push the operation switch. In the above-described latter case, however, the message is erased or limited to be partially displayed when looking at the display portion after a predetermined time lapses. Accordingly, the latter case has such an advantage as that the battery has a long duration of life, but the operability thereof is poor for the carrier.
In the above-mentioned conventional electronic watch, judgment is made upon whether the carrier wears the watch by detecting a temperature to control the displaying operation, but this method has the following problems.
In the prior art electronic watch, the method for making judgment upon whether the carrier wears the watch by detecting a change in a temperature is exclusively adopted to the electronic wristwatch which is worn around a wrist as a prevailing practice. On the other hand, the portable radio apparatus is rarely worn around the wrist. It is therefore difficult to apply the displaying method in the electronic wristwatch to the portable radio apparatus. Further, in the prior art electronic watch requires a temperature detecting function which is different from basic functions of the regular watch or the portable radio apparatus. Additional provision of a temperature detector is therefore disadvantageous for reduction in size or price.